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x86/mm: provide pmdp_establish() helper

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We need an atomic way to setup pmd page table entry, avoiding races with
CPU setting dirty/accessed bits.  This is required to implement
pmdp_invalidate() that doesn't lose these bits.

On PAE we can avoid expensive cmpxchg8b for cases when new page table
entry is not present.  If it's present, fallback to cpmxchg loop.

[akpm@linux-foundation.org: add missing `do' to do-while loop]
Link: http://lkml.kernel.org/r/20171213105756.69879-10-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2018-01-31 16:18:13 -08:00 committed by Linus Torvalds
parent a8e654f01c
commit 86fa949b05
2 changed files with 51 additions and 1 deletions
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37
arch/x86/include/asm/pgtable-3level.h
View File

@ -158,7 +158,6 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
#endif
#ifdef CONFIG_SMP
union split_pmd {
struct {
u32 pmd_low;
@ -166,6 +165,8 @@ union split_pmd {
};
pmd_t pmd;
};
#ifdef CONFIG_SMP
static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
{
union split_pmd res, *orig = (union split_pmd *)pmdp;
@ -181,6 +182,40 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
#endif
#ifndef pmdp_establish
#define pmdp_establish pmdp_establish
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp, pmd_t pmd)
{
pmd_t old;
/*
* If pmd has present bit cleared we can get away without expensive
* cmpxchg64: we can update pmdp half-by-half without racing with
* anybody.
*/
if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
union split_pmd old, new, *ptr;
ptr = (union split_pmd *)pmdp;
new.pmd = pmd;
/* xchg acts as a barrier before setting of the high bits */
old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
old.pmd_high = ptr->pmd_high;
ptr->pmd_high = new.pmd_high;
return old.pmd;
}
do {
old = *pmdp;
} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
return old;
}
#endif
#ifdef CONFIG_SMP
union split_pud {
struct {

15
arch/x86/include/asm/pgtable.h
View File

@ -1109,6 +1109,21 @@ static inline int pud_write(pud_t pud)
return pud_flags(pud) & _PAGE_RW;
}
#ifndef pmdp_establish
#define pmdp_establish pmdp_establish
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp, pmd_t pmd)
{
if (IS_ENABLED(CONFIG_SMP)) {
return xchg(pmdp, pmd);
} else {
pmd_t old = *pmdp;
*pmdp = pmd;
return old;
}
}
#endif
/*
* clone_pgd_range(pgd_t *dst, pgd_t *src, int count);
*